1. Field of the Invention
This invention relates to a driving system of the type wherein a driving screw shaft is used and one or more units can be selectively moved along the shaft, and more particularly, to a driving system for use in a slitter for slitting a sheet material such as a long, narrow strip of paper to two or more strips having predetermined widths.
2. Description of the Prior Art
In such driving system for a slitter, it is desired to easily and accurately position slitting blade or blades so that a sheet material can be slitted to two or more strips having desired widths. It is also desired that the system is simple. In Japanese Patent Application No. 107498/1978 (see Japanese Patent Application Public Disclosure No. 63473/1979), there has been proposed a slitter driving system comprising a slitter driving screw shaft, female screws meshed with the screw shaft and clutches each associated with each female screw for coupling the female screw with the slitter bracket of the corresponding slitting blade. In this system, the selective movement of the slitter blades can be effected by rotating the screw shaft and actuating only the ones of the clutches with which the slitter brackets to be desired to be moved are associated, thereby mechanically coupling the selected slitter brackets with the associated female screws to permit the female screws of the selected slitter brackets to rotate and move relatively to the screw shaft, i.e., to cause only the selected female screws and thus the selected slitter brackets to be moved along the screw shaft. This slitter driving system is very simple in structure and inexpensive, since the selective movement of the slitting blades is performed only by driving the common screw shaft and selectively actuating the clutches, as described above. However, in this driving system, the female screws tend to rotate and move relatively to the screw shaft due to inertia or friction of the female screws meshed with the screw shaft even if the associated clutches are not actuated while the screw shaft is rotated. This would lead to inaccurately positioning of the slitting blades. Moreover, this driving system needs two separate driving mechanisms for respective rotations of the slitting blades and the screw shaft.
Therefore, it is an object of this invention to provide a very simple and inexpensive driving system wherein one or more units such as slitting knives can be easily and accurately positioned.
It is another object of this invention to provide such a driving system wherein positioning of each unit and operating of each unit can be effected by way of a common driving source.